1. The Field of the Invention
This invention relates generally to optical transceivers. More specifically, exemplary embodiments of the invention are concerned with optical transceivers configured to be implemented within relatively compact components, such as host bus adapters, while maintaining compliance with established form factors and other standards.
2. Related Art
Fiber optic technology is increasingly employed as a method by which information can be reliably transmitted via a communications network. Networks employing fiber optic technology are known as optical communications networks, and are marked by high bandwidth and reliable, high-speed data transmission.
Optical communications networks employ optical transceivers in transmitting information via the network from a transmission node to a reception node. Generally, such optical transceivers implement both data signal transmission and reception capabilities, such that a transmitter portion of a transceiver converts an incoming electrical data signal into an optical data signal, while a receiver portion of the transceiver converts an incoming optical data signal into an electrical data signal.
More particularly, an optical transceiver at the transmission node receives an electrical data signal from a network device, such as a computer, and converts the electrical data signal to a modulated optical data signal using an optical transmitter such as a laser. The optical data signal can then be transmitted in a fiber optic cable via the optical communications network to a reception node of the network. Upon receipt by the reception node, the optical data signal is fed to another optical transceiver that uses a photodetector, such as a photodiode, to convert the received optical data signal back into an electrical data signal. The electrical data signal is then forwarded to a host device, such as a computer, for processing.
Generally, multiple components are designed to accomplish different aspects of these functions. For example, an optical transceiver can include one or more optical subassemblies (“OSA”) such as a transmit optical subassembly (“TOSA”), and a receive optical subassembly (“ROSA”). Typically, each OSA is created as a separate physical entity, such as a hermetically sealed cylinder that includes one or more optical sending or receiving components, as well as electrical circuitry for handling and converting the optical signals. Within the optical transceiver, each OSA generally includes electrical connections to various additional components such as a transceiver substrate, sometimes embodied in the form of a printed circuit board (“PCB”). OSAs in a conventional transceiver are generally oriented such that a longitudinal axis defined by the OSA is substantially parallel to the transceiver substrate. The transceiver substrate, in turn, is mounted to the board of a host bus adapter (“HBA”) or other component.
The transceiver substrate can include multiple other active circuitry components particularly designed to drive or handle electrical signals sent to or returning from one or more of the OSAs. Accordingly, such a transceiver substrate will usually include a number of electrical transmission lines with the one or more OSAs. Such connections may include “send” and “receive” data transmission lines for each OSA, one or more power transmission lines for each OSA, and one or more diagnostic data transmission lines for each OSA. These transmission lines are connected between the transceiver substrate and the OSA using different types of electrical connectors, examples of which include an electrical flex circuit, a direct mounting connection between conductive metallic pins extending from the OSA and solder points on the PCB, and a plug connection that extends from the PCB and mounts into electrical extensions from an OSA.
As part of ongoing efforts to reduce the size of optical transceivers and other components, manufacturing standards such as the small form factor (“SFF”), small form factor pluggable (“SFP”), and gigabit small form factor (“XFP”) standards have been developed that serve to contribute to a reduction in the overall size of optical transceivers. Nonetheless, the size of most optical transceivers, even those that comply with such manufacturing standards, best suits them for external connections to a computer system, such as a desktop computer, a laptop computer, or a handheld digital device.
Alternatively, some optical transceivers are mounted in a network panel that includes multiple optical transceivers, where the network panel is configured to include an external connection to, for example, a computer system or an Ethernet network. In these, and other, applications however, conventional optical transceivers are typically not well suited for integration within such devices.
More specifically, the number of components within the transceiver, as well as the orientation and the size of SFF or SFP optical transceivers, makes it difficult, if not impossible, to integrate conventional optical transceivers into very small spaces, such as within a pluggable card for use in a laptop computer or hand held device. For example, despite their relatively compact nature, conventional SFF, SFP, and XFP optical transceiver bodies are still too wide and/or tall to fit within a typical PCMCIA laptop envelope.
A related problem concerns the connections of the optical transceiver. In particular, use of the optical transceiver as an external, rather than internal, component necessitates the use of additional connectors and connections, which increase both the overall cost associated with the system as well as the complexity of the system. As well, optical transceivers employed in an external, rather than integrated, configuration are more prone to rough handling and damage than an integrated component.
Furthermore, even if the conventional optical transceiver could fit within such an envelope, the length of the conventional optical transceiver SFF, SFP, or XFP optical transceiver is such that the transceiver substrate takes up an inordinate amount of board space on the HBA or other component to which the optical transceiver is attached. This problem is of particular concern in light of the concurrent demands for increases in functionality and decreases in component size. These, and other, considerations make conventional optical transceivers less than ideal for integration within computer systems.
Unfortunately, typical manufacturing standards and optical transceivers have not effectively addressed these problems. This is likely due in part to the fact that typical manufacturing constraints require, among other things, a minimum number of active and passive circuitry components to be present on a transceiver substrate. Thus, a designer or manufacturer may have somewhat limited latitude in terms of the type and number of components to be included in an optical transceiver.
Other constraints along similar lines relate to engineering limitations, such that miniaturization of transceiver components becomes ever more complicated as components and mounting surfaces become smaller. Moreover, increased manufacturing and engineering difficulty also translate into higher costs.
Accordingly, what is needed are optical transceivers that can fit within relatively small envelopes such that the optical transceiver can be integrated within compact components and various computing systems and devices. At the same time, such optical transceivers should comply with established manufacturing and operational standards and requirements.